The present invention relates to devices and methods for minimally invasive pedicle screw placement, and more particularly to devices and methods that facilitate the fusion of vertebrae in the spine, for example the lumbar-sacral region of the spine during minimally invasive procedures.
In minimally invasive surgical procedures, which are becoming more and more prevalent, smaller incisions or portals are used to access the locations in the patient's body, which causes less trauma to the adjacent tissue, reduces recovery time and pain and may be performed in some cases under only local anesthesia. The avoidance of general anesthesia reduces post-operative recovery time and the risk of complications.
Minimally invasive surgical procedures are especially desirable for spine surgeries because spine pathologies are generally located in a part of the body without clear muscle planes and there exists a danger of damaging the adjacent neural and vascular tissues. For instance, in certain traditional spinal fixation procedures, the spinal muscles are stripped from the bony elements of the spine followed by laminectomy to expose the dura, the nerve roots, and the discs. The incision required to perform such a surgery has to be wide enough and the tissues have to be retracted to maintain a channel from the skin to the floor of the spinal canal that will allow direct visualization. Other non-minimally invasive fusion procedures may require more lateral tissue dissection and exposure to access the transverse processes and pedicles for placement of pedicle screws, rod constructs for stability, and bone grafts under direct vision.
To address these issues, minimally invasive spinal procedures have been developed, including in the placement of pedicle screws. One minimally invasive pedicle screw system is the MANTIS® system (“the Mantis System”) offered by Stryker Spine of Allendale, N.J. (see U.S. Pat. No. 8,002,798, the entirety of which is hereby incorporated by reference herein). In that system, elongate blades are mechanically coupled to either side of the coupling element of each pedicle screw. Each such construct is implanted within the pedicle of a vertebra through a portal or small incision, rather than a larger more invasive incision. A rod is then percutaneously guided into the coupling elements of the implanted pedicle screws with help from the attached blades, again without the need for a larger more invasive incision. This system necessarily avoids the shortcomings of more invasive pedicle screw placement systems by reducing the area required to be incised and exposed. Stryker Spine also offers another minimally invasive pedicle screw system under the name ES2® system (“the ES2 System”), which differs from the Mantis System, inter alia, in the manner in which its blades are connected to its coupling elements (see U.S. Pat. No. 8,002,798, the entirety of which has been incorporated by reference herein). In the ES2 System, blades are integrally formed with coupling elements and are broken off after proper rod placement. Yet another percutaneous system is disclosed in U.S. Pat. No. 7,250,052 (“the '052 patent”), the disclosure of which is hereby incorporated by reference herein. There, detachable members or sleeves that include channels are disclosed as being useful in guiding a rod into two or more coupling elements. These systems (as well as others) all commonly utilize extensions of some sort that extend from the pedicle screws to aid in the percutaneous placement or minimally invasive introduction of a spinal rod into coupling elements.
A problem that occurs in such minimally invasive procedures for the spine often results from the natural curvature of the spine, for instance, in the lumbar-sacral region, which causes the instruments (e.g., the aforementioned extensions) used for such procedures to obstruct one another. This problem may also exist because of or be further exacerbated in situations where a patient exhibits lordotic deformities or because of the surgical technique (e.g., the surgeon's choice of insertion angle for the instruments), the shape and overall design of the instruments, or even the patient's orientation or placement on the operating surface. Oftentimes, the outwardly extending blades or other extensions on different pedicle screws may physically cross paths or project to cross paths and therefore obstruct one another or the channels for facilitating rod insertion. This issue is hereinafter referred to as clashing, and has, to date, only been addressed by inserting the screws with the blades (such as in the case of the Mantis and ES2 Systems) or other extensions (such as in the case of other existing percutaneous pedicle screw systems) attached at modified, less optimal angles to avoid one another.
Another common challenge encountered in minimally invasive surgical procedures is the implantation and manipulation of the rod through the screw extensions. Therefore, there exists a need for new extension geometries to improve the ease of rod insertion under any of various anatomical variations.
Thus, there is a need for a percutaneous pedicle screw delivery system and methodology which avoids the aforementioned clashing problems.